Implantable neurostimulators may be used to deliver neurostimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. An implantable medical device may deliver neurostimulation therapy via leads that include electrodes located proximate to the spinal cord, pelvic nerves, stomach, or within the brain of a patient. In general, the implantable medical device delivers neurostimulation therapy in the form of electrical pulses.
A clinician selects values for a number of programmable parameters in order to define the neurostimulation therapy to be delivered to a patient. For example, the clinician selects an amplitude, which may be a current or voltage amplitude, and pulse width for a stimulation waveform to be delivered to the patient, as well as a rate at which the pulses are to be delivered to the patient. The clinician may also select particular electrodes within an electrode set to be used to deliver the pulses and the polarities of the selected electrodes. A group of parameter values may be referred to as a program in the sense that they drive the neurostimulation therapy to be delivered to the patient.
The process of selecting values for the parameters can be time consuming, and may require a great deal of trial and error before a therapeutic program is discovered. The “best” program may be a program that best balances greater clinical efficacy and minimal side effects experienced by the patient. In addition, some programs may consume less power during therapy. The clinician typically needs to test a large number of possible electrode combinations within the electrode set implanted in the patient, in order to identify an optimal combination of electrodes and associated polarities. An electrode combination is a selected subset of one or more electrodes located on one or more implantable leads coupled to an implantable neurostimulator. As a portion of the overall parameter selection process, the process of selecting electrodes and the polarities of the electrodes can be particularly time-consuming and tedious.
In some cases, the clinician may test electrode combinations by manually specifying each combination based on intuition or some idiosyncratic methodology. The clinician may then record notes on the efficacy and side effects of each combination after delivery of stimulation via that combination. In this manner, the clinician is able to later compare and select from the tested combinations. As an example of the magnitude of the task, an implantable neurostimulator commonly delivers spinal cord stimulation therapy (SCS) to a patient via two leads that include eight electrodes per lead, which equates to over 43 million potential electrode combinations.
In order to improve the efficacy of neurostimulation therapy, neurostimulators have grown in capability and complexity. Modem neurostimulators tend to have larger numbers of electrode combinations, larger parameter ranges, and the ability to simultaneously deliver multiple therapy configurations by interleaving stimulation pulses in time. Although these factors increase the clinician's ability to adjust therapy for a particular patient or disease state, the burden involved in optimizing the device parameters has similarly increased. Unfortunately, fixed reimbursement schedules and scarce clinic time present challenges to effective programming of neurostimulator therapy.